<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>随意</title>
</head>
<body>
    <p>搜索字符串"runoob",并显示匹配的起始位置：</p>
    <button onclick="myFunction()">点我</button>
    <p id="demo"></p>
    <script>
        function myFunction()
        {
            var str="visit runoob!";
            var n=str.search(/runoob/i);
            document.getElementById("demo").innerHTML=n;
        }
        </script>
        </body>
</html>